Many syringes are conventionally used. Recently there are many cases in which syringes are used by mounting them on syringe pumps respectively. Many prefilled syringes in which a medicine is filled in advance are utilized in recent years. There is a case in which the prefilled syringe is used by mounting it on the syringe pump.
In inserting the gasket into the prefilled syringe, generally used is a method so-called a vacuum plugging in which after a medicine is filled inside the outer cylinder whose opening formed at its distal end is sealed, the gasket is disposed at an opening of the outer cylinder under a pressure-decreased atmosphere (under a vacuum atmosphere), and thereafter a normal pressure state is generated to insert the gasket into the outer cylinder. In a state in which the plunger has been mounted on the gasket, it is difficult to dispose the gasket at the opening of the outer cylinder. Thus a vacuum plugging work is performed without mounting the plunger on the gasket. Therefore generally the prefilled syringe necessitates a plunger-mounting work to be performed subsequently. To make it easy to perform the work of mounting the plunger on the gasket, prevent liquid from leaking in mounting the plunger on the gasket, and decrease the amount of the work of restraining the rise of an internal pressure, generally the prefilled syringe has a mounting mechanism of mounting the plunger on the gasket by screwing a male screw portion formed on the plunger on a female screw portion formed on the gasket.
As described above, there are cases in which a medicine is given to a patient by using the syringe or the prefilled syringe by mounting them on the syringe pump. In the case where the syringe pump is used, continuous dosing of a very small amount of the medicine is performed. When the syringe pump is placed at a position higher than the patient, there is a possibility of the occurrence of a phenomenon in which the medicine is rapidly administered to the patient owing to a fall. That is, in such a state, a negative pressure is generated inside the syringe owing to the fall, and thus the gasket is sucked to the front side of the outer cylinder. The continuous dosing of a very small amount of the medicine is accomplished while a means for pressing the syringe pump fixed to the plunger is preventing the movement of the gasket caused by the sucking. When the negative pressure overcomes the engaging force acting between the plunger and the gasket, there is a danger that the gasket separates from the plunger. When the gasket separates from the plunger, the medicine inside the syringe is rapidly administered to the patient.
As syringes having a mechanism of preventing the separation of the gasket from the plunger, Japanese Patent Application Laid-Open No. 2002-272843 (patent document 1), Japanese Patent Application Laid-Open No. 2009-142508 (patent document 2), International Publication WO01-97885 (patent document 3), and Japanese Patent Application Laid-Open No. 2007-202822 (patent document 4) are listed. The patent documents 1 through 3 are proposed by the present applicant.
Syringes in which the gasket is constructed of a gasket body and a plunger-mounting member are proposed. As such syringes, for example, Japanese Utility Model Application Laid-Open No. 6-39005 (patent document 5), Japanese Patent Application Laid-Open No. 2007-44159 (patent document 6), Japanese Patent Application Laid-Open No. 2008-307237 (patent document 7), and Japanese Patent No. 3665646 (patent document 8, WO95-30444) are listed.
A syringe 1 of the patent document 1 (Japanese Patent Application Laid-Open No. 2002-272843) has an outer cylinder 2, a gasket 3 capable of sliding inside the outer cylinder 2, and a plunger 4, having the function of perform the operation of moving the gasket 3, which is inserted into the outer cylinder 2 from the opening formed at the proximal end thereof. The liquid 7 is liquid-tightly accommodated in advance inside the space surrounded with the outer cylinder 2 and the gasket 3. The flange 44 is formed at the head part 43 formed at the distal portion of the plunger 4. The gasket 3 has the hollow part. The screw thread 34 is formed on the inner surface of the proximal side of the hollow part. The space 35 for accommodating the flange 44 is formed at a portion located distally from the screw thread 34. The flange 44 which has entered the space 35 across the screw thread 34 engages the space 35 in a loosely engage state.
In this syringe, the flange 44 formed at the head part 43 of the distal portion of the plunger 4 is not screwlike. Thus when a medicine is administered to a patient by the syringe mounted on the syringe pump with the syringe pump placed at a position higher than the patient, there is a fear that the plunger separates from the gasket.
The syringe 10 of the patent document 2 (Japanese Patent Application Laid-Open No. 2009-142508) has the gasket 3, the outer cylinder 2, and the plunger 4. The plunger 4 has the spiral rib 44 formed on the outer surface of the head part 42. The gasket 3 has the spiral screwing part 33 which is to screw the spiral rib 44, the annular rib 34, for preventing the separation of the plunger from the gasket, which is located at a position in the vicinity of the spiral screwing part 33 and distal therefrom, and the accommodation part 32 for accommodating the portion where the spiral rib 44 of the head part 42 of the plunger is formed. The annular rib 34 has the rib-absent portion 35 for guiding the spiral rib 44 which has reached the annular rib owing to the progress of the screwing between the spiral rib 44 of the plunger and the spiral screwing part 33 of the gasket to the accommodation part.
This syringe is effective for preventing the separation of the plunger from the gasket. But in dependence on a manner of the work of mounting the plunger on the gasket, defective mounting of the plunger on the gasket sometimes occurs.
In the patent document 3 (International Publication WO01-97885), at the distal portion of the plunger 4, the head part (coupling portion) 43 to be inserted into the hollow part 33 of the gasket 3 and coupled to the gasket 3 is formed. A male screw 51 is formed on the outer circumferential surface of the head part 43. The female screw 52 on which the male screw 51 can be screwed is formed on the inner circumferential surface of the hollow part 33 of the gasket 3. The head part 43 has the elastic piece 61 located at a position distal from the male screw 51 and the projected portions 62, projectingly formed toward the outer circumference thereof, which are located in the vicinity of the end portions of elastic pieces 61. The ring-shaped engaging projected part 63 is formed on the inner circumferential surface of the hollow part 33 of the gasket 3 at a position distal from the female screw 52.
In this syringe, the plunger is mounted on the gasket by rotating the plunger. Thus it is necessary to perform the operation of rotating the plunger to mount the plunger on the gasket. There is a case in which a screwing operation is not properly performed. In this state, there is a possibility that the outer side surface of the gasket is not a perfect circle and thus a liquid may leak. Further a stress generated when the plunger mounted on the gasket is inclined is directly transmitted to the gasket and the liquid may leak.
The plunger used for the syringe of the patent document 4 (Japanese Patent Application Laid-Open No. 2007-202822) includes the plunger rod 22 and the gasket 21. The gasket 21 has the inner space whose distal end is closed and has an opening 212, having a smaller diameter than that of the inner space, which is formed at the proximal end thereof. The male screw-shaped projected part 223 is formed at the distal end of the plunger rod 22. When the projected part 223 enters the inner space across the opening 212, the gasket 21 and the plunger rod 22 engage each other in a free fit-on state.
The “opening having a smaller diameter” of the syringe is “not screwlike”, and necessarily has the function of preventing the plunger from dropping when the plunger is rotated reversely and in addition preventing the plunger from dropping when the plunger is pulled toward the proximal end of the syringe. Therefore the “opening having a smaller diameter” is required to have a high strength. Thus when improper screwing occurs between the projected part 223 of the plunger rod 22 and the convexity of the female screw of the gasket, the convexity screws the projected portion 223 with the convexity being twisted. As a result, the circularity of the peripheral side surface of the gasket becomes low and there is a possibility that a liquid may leak.
In the patent document 5 (Japanese Utility Model Application Laid-Open No. 6-39005), the reinforcing material 30 made of synthetic resin is fitted on the inner chamber portion of the plunger 20 closely fitted in the syringe 2 serving as a container. The reinforcing material 30 reinforces the peripheral wall portion 23 forming the inner chamber portion of the plunger 20. The plunger rod 10 is removably mounted on the reinforcing material 30. The insertion portion 16 of the plunger rod 10 is inserted into the insertion hole 34 (see FIG. 2 of the specification of the patent document 5) of the cover portion 32 of the reinforcing material 30. The plunger rod 10 is rotated to fit the opposed side 18 of the window spline 17 of the insertion portion 16 of the plunger rod 10 on the fit-on groove 36 (see FIG. 3 of the specification of the patent document 5) of the back surface 35 of the cover portion 32 of the reinforcing material 30. Thereby the mounting of the plunger rod 10 on the plunger 20 on which the reinforcing material 30 has been mounted finishes.
In this syringe, at the time the plunger-mounting work is performed, it is necessary to fit the window spline on the slit-like fit-on groove and in addition, the plunger 20 is invisible because the plunger rod stands in the way. Thus it is not easy to perform the mounting work. In addition, after the mounting work finishes, there is a danger that when the window spline is fitted on the fit-on groove, the plunger rod easily separates from the plunger.
The syringe 1 of the patent document 6 (Japanese Patent Application Laid-Open No. 2007-44159) has the outer cylinder 2, the gasket 3 capable of sliding inside the outer cylinder 2, and the plunger 4 for performing the operation of moving the gasket 3. The gasket 3 and the plunger 4 are coupled to each other by a coupling mechanism. The plunger 4 is composed of the upper plunger 41 and the lower plunger 42 fitted thereon. At the time of fitting the lower plunger 41 on the upper plunger 42, the convex portion 422 formed on the lower plunger 42 is inserted into the concave portion 412 formed on the upper plunger 41. When the convex portion 422 is inserted deep into the concave portion 412, the lower plunger 42 is rotated until the convex portion 422 formed on the lower plunger 42 is positioned at the end of the concave portion 412 formed on the upper plunger 41. At this time, the upper plunger 41 and the lower plunger 42 are engaged each other in a loosely engage state by providing the gap at the engaging portion where the upper plunger 41 and the lower plunger 42 engage each other. This syringe also necessitates a rotation operation to be performed to mount the plunger on the gasket.
In the prefilled syringe of the patent document 7 (Japanese Patent Application Laid-Open No. 2008-307237), a medicinal solution is filled therein and the gasket is plugged into the outer cylinder. The prefilled syringe includes the coupler which screws the proximal end of the gasket, the bottom rod coupled to the coupler at its proximal end, the stopper formed on the coupler, and the engaging part, formed on the bottom rod, which engages the stopper owing to the rotation of the bottom rod in the screwing direction. When the stopper contacts the engaging portion in the direction opposite to the screwing direction, the stopper elastically deforms and does not engage the engaging part.
Similarly to the syringe of the patent document 6, in this syringe, it is not easy to perform a mounting work.
The syringe of the patent document 8 (Japanese Patent No. 3665646: WO95-30444) shown in FIGS. 1 through 6 of the specification thereof has the barrel, the plunger, and the plunger rod. By driving the plunger rod, the plunger generates an axial tensile force. As a result, the diameter of the plunger decreases. With the friction between the inside of the barrel and the plunger being decreased owing to the contraction of the diameter of the plunger, the elongation of the plunger is so restricted that the sealing between the inside of the barrel and the plunger is maintained. The plunger rod has the rod member and the connection member for the plunger. The rod member is axially slidable with respect to the connection member. In the syringe of the embodiment shown in FIGS. 1 through 6 of the specification of the patent document 8, the plunger insertion part 68 has the female screw 69 which engages the male screw 71 of the plunger rod 50. The plunger rod 50 has the male screw 71 so designed that the male screw 71 engages the female screw 69 of the plunger insertion part 68. This syringe also necessitates a rotation operation to be performed to mount the plunger. The syringe of the embodiment shown in FIGS. 7 through 18 of the specification of the patent document 8 has the semicircular plunger rod distal end 164 having the convex surface projected toward the plunger. It is necessary to insert the distal end 164 into the cross-shaped slit shown in FIG. 18 and thereafter rotate the plunger. In this syringe, to mount the plunger on the plunger rod, it is necessary to perform the work placing the distal end 164 in position and inserting the distal end 164 into the slit and the operation of rotating the plunger. As shown in FIG. 11, because the distal end 164 contacts and deforms the plunger (gasket, there is a high possibility that a liquid leaks.
Similarly to the syringes of the patent documents 6 and 7, in this syringe, it is not easy to perform the mounting work and in addition there is a danger that after the plunger rod is mounted on the plunger, the plunger rod may separate from the plunger.